1. Field of the Invention:
This invention relates to a fluid handling and sampling assembly. More particularly, this invention relates to a multi-valve assembly for use in an analytical instrument.
2. Description of the Prior Art:
The heart of many analytical systems, particularly chemical analyzers which have become so popular in the last few years, is the fluid handling assembly. This assembly is designed to inject precise amounts of sample fluid along with precise amounts of various buffers or diluent into the compartments where the reaction takes place. Of prime concern in such assemblies is the precision with which small amounts of fluid can be handled. The key to their precision lies partially in the pump assembly and partially in the valve assembly.
The valve assemblies used in the original versions of such analytical devices were often complicated, expensive devices which required considerable maintenance and repair. As the precision of such devices increased, more emphasis has been placed on the ability to design reliable, care-free systems which are both inexpensive and easy to maintain.
One representative fluid handling assembly is described in U.S. Pat. No. 3,612,360 which discloses a piston pump in conjunction with a plurality of separate pistontype valves. While such a system performs quite adequately, each valve consists of a large number of parts which must be precision-milled from a suitable material such as stainless steel. Such a system is extremely expensive, and its maintenance and repair requires a considerable amount of time and effort.
The present invention relates to a fluid handling assembly of a simple design; one that is precise, simple to construct and easy to maintain.